The objective of this project is to isolate, characterize and determine the mechanism of action of certain factors, present in serum, that are required for growth and cell division of mammalian cells. Two major lines of work are anticipated during the coming year. One is the elucidation of the details of FGF (fibroblast growth factor) and insulin interaction with 3T3 cell membranes. These two polypeptide hormones control the initiation of DNA synthesis in 3T3 cells. The work planned will involve studies with isolated membrane vesicles whenever this is possible. Second is the identification of factors that control the growth of SV3T3 cells. Preliminary indications are that peptides and lipids may play important roles.